The disclosure herein relates to methods and devices for monitoring activation time within cardiac tissue to determine whether pacing therapy was effective and/or to maintain effective pacing therapy.
Implantable medical devices (IMD) are capable of utilizing pacing therapies, such as cardiac resynchronization therapy (CRT), to maintain hemodynamic benefits to patients. Pacing therapy may be delivered from an implantable generator, through a lead, and into the patient's heart. Basic programmable pacing parameters include pacing amplitude, pacing rate, pulse duration, and pacing pathway or vector (e.g., bipolar such as a lead tip electrode to a lead ring electrode, etc. or unipolar such as a lead tip electrode to IMD casing, or housing), which all may be configured to ensure effective therapy to the patient.
Retention of effective pacing (e.g., left ventricular pacing) may be beneficial in CRT. A common cause for ineffective pacing may be loss of capture due to, e.g., lead dislodgement, extracardiac stimulation, exit block, pacing from a suboptimal location, etc. Current devices may temporarily suspend, or interrupt, pacing therapy for one or more heart beats to determine if one or more pacing electrodes are effectively capturing cardiac tissue for delivery of pacing therapy. In other words, the pacing therapy is periodically interrupted to determine if effective pacing is being delivered. For example, a left ventricular (LV) capture management routine for a device employing left ventricular or biventricular pacing may involve comparison of two measured times while pacing therapy has been temporarily ceased or suspended (e.g., interrupted). The first time may be measured between a left ventricular (LV) pace and the electrical activity sensed at a right ventricular (RV) electrode with respect to the LV pace. The second time may be measured between a right atrial (RA) pace and the electrical activity sensed at a RV electrode with respect to the RA pace. The device may detect capture, or loss of capture, by comparing the first time to the second time. For example, if the second time, i.e., the RA pace to the RV sense, is less than the first time, i.e., the LV pace to the RV sense, then it may be determined that the LV pacing is ineffective.